Add step index in checkpoint name

CHANGELOG.md

@@ -17,6 +17,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 - Added multiclass AUROC metric ([#4236](https://github.com/PyTorchLightning/pytorch-lightning/pull/4236))
 
+- Added global step indexing to the checkpoint name for a better sub-epoch checkpointing experience ([#3807](https://github.com/PyTorchLightning/pytorch-lightning/pull/3807)) 
+
 ### Changed
 
 - W&B log in sync with Trainer step ([#4405](https://github.com/PyTorchLightning/pytorch-lightning/pull/4405))

pytorch_lightning/callbacks/model_checkpoint.py

@@ -101,7 +101,7 @@ class ModelCheckpoint(Callback):
                 ...     filename='{epoch}-{val_loss:.2f}-{other_metric:.2f}'
                 ... )
 
-            By default, filename is ``None`` and will be set to ``'{epoch}'``.
+            By default, filename is ``None`` and will be set to ``'{epoch}-{step}'``.
 
 
     Example::
@@ -222,16 +222,16 @@ def save_checkpoint(self, trainer, pl_module):
         monitor_candidates = self._monitor_candidates(trainer)
 
         # ie: path/val_loss=0.5.ckpt
-        filepath = self._get_metric_interpolated_filepath_name(epoch, monitor_candidates)
+        filepath = self._get_metric_interpolated_filepath_name(monitor_candidates, epoch, global_step)
 
         # callback supports multiple simultaneous modes
         # here we call each mode sequentially
         # Mode 1: save all checkpoints OR only the top k
         if self.save_top_k:
-            self._save_top_k_checkpoints(monitor_candidates, trainer, pl_module, epoch, filepath)
+            self._save_top_k_checkpoints(monitor_candidates, trainer, pl_module, filepath)
 
         # Mode 2: save the last checkpoint
-        self._save_last_checkpoint(trainer, pl_module, epoch, monitor_candidates, filepath)
+        self._save_last_checkpoint(trainer, pl_module, monitor_candidates, filepath)
 
     def __validate_init_configuration(self):
         if self.save_top_k is not None and self.save_top_k < -1:
@@ -360,16 +360,17 @@ def _format_checkpoint_name(
         cls,
         filename: Optional[str],
         epoch: int,
+        step: int,
         metrics: Dict[str, Any],
         prefix: str = "",
     ) -> str:
         if not filename:
             # filename is not set, use default name
-            filename = "{epoch}"
+            filename = "{epoch}-{step}"
         # check and parse user passed keys in the string
         groups = re.findall(r"(\{.*?)[:\}]", filename)
         if len(groups) >= 0:
-            metrics["epoch"] = epoch
+            metrics.update({"epoch": epoch, 'step': step})
             for group in groups:
                 name = group[1:]
                 filename = filename.replace(group, name + "={" + name)
@@ -379,32 +380,32 @@ def _format_checkpoint_name(
         return cls.CHECKPOINT_JOIN_CHAR.join([txt for txt in (prefix, filename) if txt])
 
     def format_checkpoint_name(
-        self, epoch: int, metrics: Dict[str, Any], ver: Optional[int] = None
+        self, epoch: int, step: int, metrics: Dict[str, Any], ver: Optional[int] = None
     ) -> str:
         """Generate a filename according to the defined template.
 
         Example::
 
             >>> tmpdir = os.path.dirname(__file__)
             >>> ckpt = ModelCheckpoint(dirpath=tmpdir, filename='{epoch}')
-            >>> os.path.basename(ckpt.format_checkpoint_name(0, {}))
+            >>> os.path.basename(ckpt.format_checkpoint_name(0, 1, metrics={}))
             'epoch=0.ckpt'
             >>> ckpt = ModelCheckpoint(dirpath=tmpdir, filename='{epoch:03d}')
-            >>> os.path.basename(ckpt.format_checkpoint_name(5, {}))
+            >>> os.path.basename(ckpt.format_checkpoint_name(5, 2, metrics={}))
             'epoch=005.ckpt'
             >>> ckpt = ModelCheckpoint(dirpath=tmpdir, filename='{epoch}-{val_loss:.2f}')
-            >>> os.path.basename(ckpt.format_checkpoint_name(2, dict(val_loss=0.123456)))
+            >>> os.path.basename(ckpt.format_checkpoint_name(2, 3, metrics=dict(val_loss=0.123456)))
             'epoch=2-val_loss=0.12.ckpt'
             >>> ckpt = ModelCheckpoint(dirpath=tmpdir, filename='{missing:d}')
-            >>> os.path.basename(ckpt.format_checkpoint_name(0, {}))
+            >>> os.path.basename(ckpt.format_checkpoint_name(0, 4, metrics={}))
             'missing=0.ckpt'
-            >>> ckpt = ModelCheckpoint(filename='{epoch}')
-            >>> os.path.basename(ckpt.format_checkpoint_name(0, {}))
-            'epoch=0.ckpt'
+            >>> ckpt = ModelCheckpoint(filename='{step}')
+            >>> os.path.basename(ckpt.format_checkpoint_name(0, 0, {}))
+            'step=0.ckpt'
 
         """
         filename = self._format_checkpoint_name(
-            self.filename, epoch, metrics, prefix=self.prefix
+            self.filename, epoch, step, metrics, prefix=self.prefix
         )
         if ver is not None:
             filename = self.CHECKPOINT_JOIN_CHAR.join((filename, f"v{ver}"))
@@ -479,13 +480,11 @@ def _validate_monitor_key(self, trainer):
             )
             raise MisconfigurationException(m)
 
-    def _get_metric_interpolated_filepath_name(self, epoch, ckpt_name_metrics):
-        filepath = self.format_checkpoint_name(epoch, ckpt_name_metrics)
+    def _get_metric_interpolated_filepath_name(self, ckpt_name_metrics: Dict[str, Any], epoch: int, step: int):
+        filepath = self.format_checkpoint_name(epoch, step, ckpt_name_metrics)
         version_cnt = 0
         while self._fs.exists(filepath):
-            filepath = self.format_checkpoint_name(
-                epoch, ckpt_name_metrics, ver=version_cnt
-            )
+            filepath = self.format_checkpoint_name(epoch, step, ckpt_name_metrics, ver=version_cnt)
             # this epoch called before
             version_cnt += 1
         return filepath
@@ -494,9 +493,10 @@ def _monitor_candidates(self, trainer):
         ckpt_name_metrics = deepcopy(trainer.logger_connector.logged_metrics)
         ckpt_name_metrics.update(trainer.logger_connector.callback_metrics)
         ckpt_name_metrics.update(trainer.logger_connector.progress_bar_metrics)
+        ckpt_name_metrics.update({"step": trainer.global_step, "epoch": trainer.current_epoch})
         return ckpt_name_metrics
 
-    def _save_last_checkpoint(self, trainer, pl_module, epoch, ckpt_name_metrics, filepath):
+    def _save_last_checkpoint(self, trainer, pl_module, ckpt_name_metrics, filepath):
         should_save_last = self.monitor is None or self.save_last
         if not should_save_last:
             return
@@ -506,7 +506,11 @@ def _save_last_checkpoint(self, trainer, pl_module, epoch, ckpt_name_metrics, fi
         # when user ALSO asked for the 'last.ckpt' change the name
         if self.save_last:
             last_filepath = self._format_checkpoint_name(
-                self.CHECKPOINT_NAME_LAST, epoch, ckpt_name_metrics, prefix=self.prefix
+                self.CHECKPOINT_NAME_LAST,
+                trainer.current_epoch,
+                trainer.global_step,
+                ckpt_name_metrics,
+                prefix=self.prefix
             )
             last_filepath = os.path.join(self.dirpath, f"{last_filepath}.ckpt")
 
@@ -523,17 +527,19 @@ def _save_last_checkpoint(self, trainer, pl_module, epoch, ckpt_name_metrics, fi
         if self.monitor is None:
             self.best_model_path = self.last_model_path
 
-    def _save_top_k_checkpoints(self, metrics, trainer, pl_module, epoch, filepath):
+    def _save_top_k_checkpoints(self, metrics, trainer, pl_module, filepath):
         current = metrics.get(self.monitor)
+        epoch = metrics.get("epoch")
+        step = metrics.get("step")
 
         if not isinstance(current, torch.Tensor) and current is not None:
             current = torch.tensor(current, device=pl_module.device)
 
         if self.check_monitor_top_k(current):
-            self._update_best_and_save(filepath, current, epoch, trainer, pl_module)
+            self._update_best_and_save(filepath, current, epoch, step, trainer, pl_module)
         elif self.verbose:
             rank_zero_info(
-                f"Epoch {epoch:d}: {self.monitor} was not in top {self.save_top_k}"
+                f"Epoch {epoch:d}, step {step:d}: {self.monitor} was not in top {self.save_top_k}"
             )
 
     def _is_valid_monitor_key(self, metrics):
@@ -544,11 +550,11 @@ def _update_best_and_save(
         filepath: str,
         current: torch.Tensor,
         epoch: int,
+        step: int,
         trainer,
         pl_module,
     ):
-
-        k = epoch + 1 if self.save_top_k == -1 else self.save_top_k
+        k = len(self.best_k_models) + 1 if self.save_top_k == -1 else self.save_top_k
 
         del_list = []
         if len(self.best_k_models) == k and k > 0:
@@ -575,9 +581,8 @@ def _update_best_and_save(
 
         if self.verbose:
             rank_zero_info(
-                f"Epoch {epoch:d}: {self.monitor} reached"
-                f" {current:0.5f} (best {self.best_model_score:0.5f}),"
-                f" saving model to {filepath} as top {k}"
+                f"Epoch {epoch:d}, global step {step:d}: {self.monitor} reached {current:0.5f} (best {self.best_model_score:0.5f}),"
+                f' saving model to "{filepath}" as top {k}'
             )
         self._save_model(filepath, trainer, pl_module)
 

pytorch_lightning/trainer/evaluation_loop.py

@@ -250,9 +250,10 @@ def __run_eval_epoch_end(self, num_dataloaders, using_eval_result):
         # depre warning
         if eval_results is not None and user_reduced:
             step = 'testing_epoch_end' if self.testing else 'validation_epoch_end'
-            m = f'The {step} should not return anything as of 9.1.' \
-                f'to log, use self.log(...) or self.write(...) directly in the LightningModule'
-            self.warning_cache.warn(m)
+            self.warning_cache.warn(
+                f'The {step} should not return anything as of 9.1.'
+                ' To log, use self.log(...) or self.write(...) directly in the LightningModule'
+            )
 
         if using_eval_result and not user_reduced:
             eval_results = self.__auto_reduce_result_objs(outputs)